U.S. patent application number 13/782142 was filed with the patent office on 2013-07-11 for dual parallel amplifier based dc-dc converter.
This patent application is currently assigned to RF MICRO DEVICES, INC.. The applicant listed for this patent is RF Micro Devices, Inc.. Invention is credited to Andrew F. Folkmann, Philippe Gorisse, Michael R. Kay, Nadim Khlat.
Application Number | 20130176075 13/782142 |
Document ID | / |
Family ID | 48743496 |
Filed Date | 2013-07-11 |
United States Patent
Application |
20130176075 |
Kind Code |
A1 |
Kay; Michael R. ; et
al. |
July 11, 2013 |
DUAL PARALLEL AMPLIFIER BASED DC-DC CONVERTER
Abstract
A direct current (DC)-DC converter, which includes switching
circuitry, a first parallel amplifier, and a second parallel
amplifier, is disclosed. The switching circuitry has a switching
circuitry output. The first parallel amplifier has a first feedback
input and a first parallel amplifier output. The second parallel
amplifier has a second feedback input and a second parallel
amplifier output. A first inductive element is coupled between the
switching circuitry output and the first feedback input. A second
inductive element is coupled between the first feedback input and
the second feedback input.
Inventors: |
Kay; Michael R.;
(Summerfield, NC) ; Folkmann; Andrew F.; (Cedar
Rapids, IA) ; Khlat; Nadim; (Cugnaux, FR) ;
Gorisse; Philippe; (Brax, FR) |
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Applicant: |
Name |
City |
State |
Country |
Type |
RF Micro Devices, Inc.; |
Greensboro |
NC |
US |
|
|
Assignee: |
RF MICRO DEVICES, INC.
Greensboro
NC
|
Family ID: |
48743496 |
Appl. No.: |
13/782142 |
Filed: |
March 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13661552 |
Oct 26, 2012 |
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13782142 |
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61605267 |
Mar 1, 2012 |
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61551596 |
Oct 26, 2011 |
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61562493 |
Nov 22, 2011 |
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Current U.S.
Class: |
330/127 ;
323/234 |
Current CPC
Class: |
H03F 3/24 20130101; H03F
1/02 20130101; H03F 2200/432 20130101; H03F 2200/555 20130101; H03F
3/195 20130101; G05F 1/46 20130101; H03F 1/0266 20130101 |
Class at
Publication: |
330/127 ;
323/234 |
International
Class: |
G05F 1/46 20060101
G05F001/46; H03F 1/02 20060101 H03F001/02 |
Claims
1. Circuitry comprising: switching circuitry having a switching
circuitry output; a first parallel amplifier having a first
feedback input and a first parallel amplifier output, such that a
first inductive element is coupled between the switching circuitry
output and the first feedback input; and a second parallel
amplifier having a second feedback input and a second parallel
amplifier output, such that a second inductive element is coupled
between the first feedback input and the second feedback input.
2. The circuitry of claim 1 further comprising the first inductive
element and the second inductive element.
3. The circuitry of claim 1 wherein the first feedback input is
coupled to the first parallel amplifier output and the second
feedback input is coupled to the second parallel amplifier
output.
4. The circuitry of claim 1 wherein: the first parallel amplifier
is adapted to partially provide a first power supply output signal
via the first parallel amplifier output and the second inductive
element based on a voltage setpoint; the second parallel amplifier
is adapted to partially provide the first power supply output
signal via the second parallel amplifier output based on the
voltage setpoint; and the switching circuitry is adapted to
partially provide the first power supply output signal via the
first inductive element and the second inductive element.
5. The circuitry of claim 4 wherein a maximum output current from
the first parallel amplifier is at least ten times greater than a
maximum output current from the second parallel amplifier.
6. The circuitry of claim 4 wherein the voltage setpoint is based
on a power supply control signal.
7. The circuitry of claim 4 wherein: the first parallel amplifier
is further adapted to partially regulate a voltage of the first
power supply output signal based on the voltage setpoint; the
second parallel amplifier is further adapted to partially regulate
the voltage of the first power supply output signal based on the
voltage setpoint; and the switching circuitry is further adapted to
regulate the first power supply output signal to about minimize an
output current from the first parallel amplifier.
8. The circuitry of claim 4 further comprising a radio frequency
(RF) power amplifier (PA), wherein: the first power supply output
signal is a first envelope power supply signal; and the RF PA is
adapted to receive and amplify an RF input signal to provide an RF
transmit signal using the first envelope power supply signal.
9. The circuitry of claim 8 wherein the first envelope power supply
signal provides power for amplification to the RF PA.
10. The circuitry of claim 8 wherein the RF PA comprises a final
stage adapted to provide the RF transmit signal using the first
envelope power supply signal.
11. The circuitry of claim 4 wherein: a DC power source is adapted
to provide a DC source signal to the first parallel amplifier, to
the second parallel amplifier, and to the switching circuitry; the
first parallel amplifier is further adapted to partially provide
the first power supply output signal using the DC source signal;
the second parallel amplifier is further adapted to partially
provide the first power supply output signal using the DC source
signal; and the switching circuitry is further adapted to partially
provide the first power supply output signal using the DC source
signal.
12. The circuitry of claim 11 wherein the DC power source is a
battery.
13. The circuitry of claim 11 further comprising the DC power
source.
14. The circuitry of claim 4 wherein: the first inductive element
and the second inductive element are coupled to one another at a
first connection node; and the first inductive element and the
second inductive element are adapted to provide a second power
supply output signal via the first connection node.
15. The circuitry of claim 1 further comprising a first offset
capacitive element and a second offset capacitive element wherein:
the first offset capacitive element is coupled between the first
feedback input and the first parallel amplifier output; and the
second offset capacitive element is coupled between the second
feedback input and the second parallel amplifier output.
16. The circuitry of claim 1 wherein the first inductive element
has a first inductance and the second inductive element has a
second inductance, such that a magnitude of the first inductance is
at least three times greater than a magnitude of the second
inductance.
17. The circuitry of claim 1 wherein a third inductive element is
coupled between the first parallel amplifier output and the first
feedback input.
18. The circuitry of claim 17 wherein: the first parallel amplifier
is adapted to partially provide a first power supply output signal
via the first parallel amplifier output based on a voltage
setpoint; and a phase-shift across the third inductive element at
least partially compensates for limited open loop gain of the first
parallel amplifier at frequencies above a first frequency
threshold.
19. The circuitry of claim 17 wherein the first inductive element
has a first inductance, the second inductive element has a second
inductance, and the third inductive element has a third inductance,
such that a magnitude of the first inductance is at least ten times
greater than a magnitude of the third inductance.
20. The circuitry of claim 19 wherein the magnitude of the first
inductance is at least three times greater than a magnitude of the
second inductance.
21. The circuitry of claim 17 wherein a fourth inductive element is
coupled between the second parallel amplifier output and the second
feedback input.
22. The circuitry of claim 21 wherein: the first parallel amplifier
is adapted to partially provide a first power supply output signal
via the first parallel amplifier output based on a voltage
setpoint; the second parallel amplifier is adapted to partially
provide the first power supply output signal via the second
parallel amplifier output based on the voltage setpoint; a
phase-shift across the third inductive element at least partially
compensates for limited open loop gain of the first parallel
amplifier at frequencies above a first frequency threshold; and a
phase-shift across the fourth inductive element at least partially
compensates for limited open loop gain of the second parallel
amplifier at frequencies above a second frequency threshold.
23. The circuitry of claim 21 wherein the first inductive element
has a first inductance, the second inductive element has a second
inductance, the third inductive element has a third inductance, and
the fourth inductive element has a fourth inductance, such that a
magnitude of the second inductance is at least ten times greater
than a magnitude of the fourth inductance.
24. The circuitry of claim 23 wherein a magnitude of the first
inductance is at least three times greater than the magnitude of
the second inductance.
25. Circuitry comprising: switching circuitry having a switching
circuitry output; a first parallel amplifier having a first
feedback input and a first parallel amplifier output, such that a
first inductive element is coupled between the switching circuitry
output and the first feedback input; and a second parallel
amplifier having a second feedback input and a second parallel
amplifier output, such that a second inductive element and a third
inductive element are coupled in series between the first feedback
input and the second feedback input.
26. A method comprising: partially providing a first power supply
output signal via a series combination of a first inductive element
and a second inductive element; partially providing the first power
supply output signal via a first parallel amplifier output based on
a voltage setpoint and feeding back a voltage to a first feedback
input from a first connection node between the first inductive
element and the second inductive element; and partially providing
the first power supply output signal via a second parallel
amplifier output based on the voltage setpoint and feeding back a
voltage to a second feedback input from the second inductive
element.
Description
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application No. 61/605,267, filed Mar. 1, 2012.
[0002] The present application claims priority to and is a
continuation-in-part of U.S. patent application Ser. No.
13/661,552, filed Oct. 26, 2012, entitled "INDUCTANCE BASED
PARALLEL AMPLIFIER PHASE COMPENSATION," which claims priority to
U.S. Provisional Patent Applications No. 61/551,596, filed Oct. 26,
2011, and No. 61/562,493, filed Nov. 22, 2011.
[0003] All of the applications listed above are hereby incorporated
herein by reference in their entireties.
FIELD OF THE DISCLOSURE
[0004] The present disclosure relates to direct current (DC)-DC
converters and circuits that use DC-DC converters.
BACKGROUND
[0005] DC-DC converters often include switching power supplies,
which may be based on switching at least one end of an energy
storage element, such as an inductor, between a source of DC
voltage and a ground. As a result, an output voltage from a DC-DC
converter may have a ripple voltage resulting from the switching
associated with the energy storage element. Typically, the ripple
voltage is undesirable and is minimized as much as sizes and costs
permit. Thus, there is a need to minimize ripple voltage using
techniques that minimize sizes and costs.
SUMMARY
[0006] A direct current (DC)-DC converter, which includes switching
circuitry, a first parallel amplifier, and a second parallel
amplifier, is disclosed. The switching circuitry has +a switching
circuitry output. The first parallel amplifier has a first feedback
input and a first parallel amplifier output. The second parallel
amplifier has a second feedback input and a second parallel
amplifier output. A first inductive element is coupled between the
switching circuitry output and the first feedback input. A second
inductive element is coupled between the first feedback input and
the second feedback input.
[0007] In one embodiment of the DC-DC converter, the first parallel
amplifier partially provides a first power supply output signal via
the first parallel amplifier output and the second inductive
element based on a voltage setpoint. The second parallel amplifier
partially provides the first power supply output signal via the
second parallel amplifier output based on the voltage setpoint. The
switching supply partially provides the first power supply output
signal via the first inductive element and the second inductive
element. The switching supply may provide power more efficiently
than the first parallel amplifier and the second parallel
amplifier. However, due to switching transients, ripple, and
latency in the switching supply, the first parallel amplifier may
at least partially provide a voltage of the first power supply
output signal more accurately than the switching supply. Further,
since the second inductive element is coupled between the first
parallel amplifier output and the second parallel amplifier output,
the second parallel amplifier is somewhat de-coupled from the
ripple current of the first inductive element. As such, the second
parallel amplifier may at least partially provide the voltage of
the first power supply output signal more accurately than the first
parallel amplifier due to bandwidth limitations of the first
parallel amplifier. Further, by including the second inductive
element, the second parallel amplifier may be significantly smaller
than the first parallel amplifier, thereby having minimal impact on
size, cost, and efficiency of the DC-DC converter.
[0008] In one embodiment of the DC-DC converter, the first parallel
amplifier partially regulates the voltage of the first power supply
output signal based on the voltage setpoint of the first power
supply output signal, and the second parallel amplifier partially
regulates the voltage of the first power supply output signal based
on the voltage setpoint of the first power supply output signal. In
this regard, an output current from the first parallel amplifier is
used to drive the voltage of the first power supply output signal
toward a desired voltage of the first power supply output signal.
Further, an output current from the second parallel amplifier is
used to drive the voltage of the first power supply output signal
toward the desired voltage of the first power supply output signal.
In this regard, in one embodiment of the DC-DC converter, the
switching supply provides current to regulate the first power
supply output signal to reduce the output current from the first
parallel amplifier, to reduce the output current from the second
parallel amplifier, or both, to increase efficiency of the DC-DC
converter. In this regard, the first and the second parallel
amplifiers may behave like voltage sources and the switching supply
may behave like a current source.
[0009] In one embodiment of the DC-DC converter, the switching
supply regulates the first power supply output signal to about
minimize the output current from the first parallel amplifier. In
an alternate embodiment of the DC-DC converter, the switching
supply regulates the first power supply output signal to about
minimize the output current from the second parallel amplifier. In
an additional embodiment of the DC-DC converter, the switching
supply regulates the first power supply output signal to reduce the
output current from the first parallel amplifier and to reduce the
output current from the second parallel amplifier.
[0010] In one embodiment of the DC-DC converter, the DC-DC
converter functions as an envelope tracking power supply, which
provides power to a radio frequency (RF) power amplifier (PA). As
such, the first power supply output signal is a first envelope
power supply signal. In envelope tracking systems, the first
envelope power supply signal is amplitude modulated to track an
envelope of an RF transmit signal provided by the RF PA. As RF
communications protocols evolve, a bandwidth of the envelope of the
RF transmit signal and a correlated bandwidth of the first envelope
power supply signal tend to increase to support increasing data
bandwidths. In this regard, the DC-DC converter must support such
increasing bandwidths. Further, as RF communications protocols
evolve, limits on out-of-band RF emissions may become increasingly
stringent. Therefore, voltage accuracy of the first power supply
output signal may become increasingly important.
[0011] Those skilled in the art will appreciate the scope of the
disclosure and realize additional aspects thereof after reading the
following detailed description in association with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings incorporated in and forming a part
of this specification illustrate several aspects of the disclosure,
and together with the description serve to explain the principles
of the disclosure.
[0013] FIG. 1 shows a direct current (DC)-DC converter according to
one embodiment of the present disclosure.
[0014] FIG. 2 shows the DC-DC converter according to an alternate
embodiment of the DC-DC converter.
[0015] FIG. 3 shows the DC-DC converter according to an additional
embodiment of the DC-DC converter.
[0016] FIG. 4 shows the DC-DC converter according to another
embodiment of the DC-DC converter.
[0017] FIG. 5 shows the DC-DC converter according to a further
embodiment of the DC-DC converter.
[0018] FIG. 6 shows the DC-DC converter according to a supplemental
embodiment of the DC-DC converter.
[0019] FIG. 7 shows a radio frequency (RF) communications system
according to one embodiment of the present disclosure.
[0020] FIG. 8 shows the RF communications system according to an
alternate embodiment of the RF communications system.
[0021] FIG. 9 shows the RF communications system according to an
additional embodiment of the RF communications system.
[0022] FIG. 10 shows the RF communications system according to
another embodiment of the RF communications system.
DETAILED DESCRIPTION
[0023] The embodiments set forth below represent the necessary
information to enable those skilled in the art to practice the
disclosure and illustrate the best mode of practicing the
disclosure. Upon reading the following description in light of the
accompanying drawings, those skilled in the art will understand the
concepts of the disclosure and will recognize applications of these
concepts not particularly addressed herein. It should be understood
that these concepts and applications fall within the scope of the
disclosure and the accompanying claims.
[0024] A direct current (DC)-DC converter, which includes switching
circuitry, a first parallel amplifier, and a second parallel
amplifier, is disclosed. The switching circuitry has a switching
circuitry output. The first parallel amplifier has a first feedback
input and a first parallel amplifier output. The second parallel
amplifier has a second feedback input and a second parallel
amplifier output. A first inductive element is coupled between the
switching circuitry output and the first feedback input. A second
inductive element is coupled between the first feedback input and
the second feedback input.
[0025] FIG. 1 shows a DC-DC converter 10 according to one
embodiment of the present disclosure. The DC-DC converter 10
includes a switching supply 12, a first parallel amplifier 14, and
a second parallel amplifier 16. The switching supply 12 includes
switching circuitry 18, a first inductive element L1, and a second
inductive element L2. In an alternate embodiment of the DC-DC
converter 10, the first inductive element L1, the second inductive
element L2, or both are provided externally to the DC-DC converter
10. The first parallel amplifier 14 has a first feedback input FBI1
and a first parallel amplifier output PAO1. The second parallel
amplifier 16 has a second feedback input FBI2 and a second parallel
amplifier output PAO2. The switching circuitry 18 has a switching
circuitry output SCO.
[0026] The first inductive element L1 is coupled between the
switching circuitry output SCO and the first feedback input FBI1.
The second inductive element L2 is coupled between the first
feedback input FBI1 and the second feedback input FBI2. The first
feedback input FBI1 is coupled to the first parallel amplifier
output PAO1. The second feedback input FBI2 is coupled to the
second parallel amplifier output PAO2.
[0027] The first parallel amplifier 14 provides a first parallel
amplifier output current IP1 via the first parallel amplifier
output PAO1. The second parallel amplifier 16 provides a second
parallel amplifier output current IP2 via the second parallel
amplifier output PAO2. The switching circuitry 18 provides a
switching output voltage VS via the switching circuitry output SCO.
The first inductive element L1 has a first inductor current IL1 and
a first inductance. The second inductive element L2 has a second
inductor current 1L2 and a second inductance. In one embodiment of
the switching supply 12, a first connection node 20 is provided
where the first inductive element L1 and the second inductive
element L2 are connected to one another. The first connection node
20 provides a second voltage V2 to the first parallel amplifier 14
via the first feedback input FBI1. In general, the first inductive
element L1 and the second inductive element L2 are coupled to one
another at the first connection node 20.
[0028] In one embodiment of the DC-DC converter 10, the first
parallel amplifier 14 partially provides a first power supply
output signal PS1 via the first parallel amplifier output PAO1 and
the second inductive element L2 based on a voltage setpoint. The
first power supply output signal PS1 has a first voltage V1.
Further, the second parallel amplifier 16 partially provides the
first power supply output signal PS1 via the second parallel
amplifier output PAO2 based on the voltage setpoint. Additionally,
the switching circuitry 18 partially provides the first power
supply output signal PS1 via the first inductive element L1 and the
second inductive element L2.
[0029] The switching circuitry 18 may provide power more
efficiently than the first parallel amplifier 14 and the second
parallel amplifier 16. However, due to switching transients,
ripple, and latency in the switching circuitry 18, the first
parallel amplifier 14 may at least partially provide the first
voltage V1 more accurately than the switching circuitry 18.
Further, since the second inductive element L2 is coupled between
the first parallel amplifier output PAO1 and the second parallel
amplifier output PAO2, the second parallel amplifier 16 is somewhat
de-coupled from the ripple current of the first inductive element
L1. As such, the second parallel amplifier 16 may at least
partially provide the first voltage V1 more accurately than the
first parallel amplifier 14 due to bandwidth limitations of the
first parallel amplifier 14. Further, by including the second
inductive element L2, the second parallel amplifier 16 may be
significantly smaller than the first parallel amplifier 14, thereby
having minimal impact on size, cost, and efficiency of the DC-DC
converter 10.
[0030] In one embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, a size of the first parallel
amplifier 14 is at least two times greater than a size of the
second parallel amplifier 16. In an alternate embodiment of the
first parallel amplifier 14 and the second parallel amplifier 16,
the size of the first parallel amplifier 14 is at least five times
greater than the size of the second parallel amplifier 16. In an
additional embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, the size of the first parallel
amplifier 14 is at least ten times greater than the size of the
second parallel amplifier 16. In another embodiment of the first
parallel amplifier 14 and the second parallel amplifier 16, the
size of the first parallel amplifier 14 is at least twenty times
greater than the size of the second parallel amplifier 16. In a
further embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, the size of the first parallel
amplifier 14 is at least fifty times greater than the size of the
second parallel amplifier 16. In a supplementary embodiment of the
first parallel amplifier 14 and the second parallel amplifier 16,
the size of the first parallel amplifier 14 is less than 100 times
greater than the size of the second parallel amplifier 16.
[0031] In one embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, a maximum output current from the
first parallel amplifier 14 is at least two times greater than a
maximum output current from the second parallel amplifier 16. In an
alternate embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, the maximum output current from the
first parallel amplifier 14 is at least five times greater than the
maximum output current from the second parallel amplifier 16. In an
additional embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, the maximum output current from the
first parallel amplifier 14 is at least ten times greater than the
maximum output current from the second parallel amplifier 16. In
another embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, the maximum output current from the
first parallel amplifier 14 is at least twenty times greater than
the maximum output current from the second parallel amplifier 16.
In a further embodiment of the first parallel amplifier 14 and the
second parallel amplifier 16, the maximum output current from the
first parallel amplifier 14 is at least fifty times greater than
the maximum output current from the second parallel amplifier 16.
In a supplementary embodiment of the first parallel amplifier 14
and the second parallel amplifier 16, the maximum output current
from the first parallel amplifier 14 is less than 100 times greater
than the maximum output current from the second parallel amplifier
16.
[0032] In one embodiment of the first inductive element L1 and the
second inductive element L2, the first inductance is at least two
times greater than the second inductance. In an alternate
embodiment of the first inductive element L1 and the second
inductive element L2, the first inductance is at least three times
greater than the second inductance. In an additional embodiment of
the first inductive element L1 and the second inductive element L2,
the first inductance is at least five times greater than the second
inductance. In another embodiment of the first inductive element L1
and the second inductive element L2, the first inductance is at
least ten times greater than the second inductance. In a further
embodiment of the first inductive element L1 and the second
inductive element L2, the first inductance is at least twenty times
greater than the second inductance. In an exemplary embodiment of
the first inductive element L1 and the second inductive element L2,
the first inductance is equal to about 500 nano-henries and the
second inductance is equal to about 100 nano-henries.
[0033] In one embodiment of the DC-DC converter 10, the first
parallel amplifier 14 partially regulates the voltage, which is the
first voltage V1, of the first power supply output signal PS1 based
on the voltage setpoint of the first power supply output signal
PS1. The second parallel amplifier 16 partially regulates the
voltage of the first power supply output signal PS1 based on the
voltage setpoint of the first power supply output signal PS1. In
this regard, the output current, called the first parallel
amplifier output current IP1, from the first parallel amplifier 14
is used to drive the voltage of the first power supply output
signal PS1 toward a desired voltage of the first power supply
output signal PS1.
[0034] Further, the output current, called the second parallel
amplifier output current IP2, from the second parallel amplifier 16
is used to drive the voltage of the first power supply output
signal PS1 toward the desired voltage of the first power supply
output signal PS1. In this regard, in one embodiment of the DC-DC
converter 10, the switching circuitry 18 provides current to
regulate the first power supply output signal PS1 to reduce the
output current from the first parallel amplifier 14, to reduce the
output current from the second parallel amplifier 16, or both, to
increase efficiency of the DC-DC converter 10. In this regard, the
first and the second parallel amplifiers 14, 16 may behave like
voltage sources and the switching circuitry 18 may behave like a
current source.
[0035] In one embodiment of the DC-DC converter 10, the switching
circuitry 18 regulates the first power supply output signal PS1 to
about minimize the output current from the first parallel amplifier
14. In an alternate embodiment of the DC-DC converter 10, the
switching circuitry 18 regulates the first power supply output
signal PS1 to about minimize the output current from the second
parallel amplifier 16. In an additional embodiment of the DC-DC
converter 10, the switching circuitry 18 regulates the first power
supply output signal PS1 to reduce the output current from the
first parallel amplifier 14 and to reduce the output current from
the second parallel amplifier 16.
[0036] In one embodiment of the DC-DC converter 10, the DC-DC
converter 10 receives a DC source signal VDC, such that the first
parallel amplifier 14 partially provides the first power supply
output signal PS1 using the DC source signal VDC, the second
parallel amplifier 16 partially provides the first power supply
output signal PS1 using the DC source signal VDC, and the switching
circuitry 18 partially provides the first power supply output
signal PS1 using the DC source signal VDC.
[0037] FIG. 2 shows the DC-DC converter 10 according to an
alternate embodiment of the DC-DC converter 10. The DC-DC converter
10 illustrated in FIG. 2 is similar to the DC-DC converter 10
illustrated in FIG. 1, except the DC-DC converter 10 illustrated in
FIG. 2 further includes power supply control circuitry 22, a first
offset capacitive element CO1, and a second offset capacitive
element CO2. Additionally, the switching supply 12 further includes
a first low-pass filter 24 and a second low-pass filter 26. The
first low-pass filter 24 includes the first inductive element L1
and a first filter capacitive element C1. The second low-pass
filter 26 includes the second inductive element L2 and a second
filter capacitive element C2.
[0038] The first offset capacitive element CO1 is coupled between
the first parallel amplifier output PAO1 and the second inductive
element L2, such that the first parallel amplifier 14 partially
provides the first power supply output signal PS1 via the first
parallel amplifier output PAO1, the first offset capacitive element
CO1, and the second inductive element L2 based on the voltage
setpoint. As such, the first offset capacitive element CO1 is
coupled between the first feedback input FBI1 and the first
parallel amplifier output PAO1. The first offset capacitive element
CO1 allows the second voltage V2 to be higher than a voltage at the
first parallel amplifier output PAO1. As a result, the first
parallel amplifier 14 may at least partially regulate the first
voltage V1 in a proper manner even if the second voltage V2 is
greater than a maximum output voltage from the first parallel
amplifier 14 at the first parallel amplifier output PAO1.
[0039] The second offset capacitive element CO2 is coupled between
the second parallel amplifier output PAO2 and the second feedback
input FBI2, such that the second parallel amplifier 16 partially
provides the first power supply output signal PS1 via the second
parallel amplifier output PAO2 and the second offset capacitive
element CO2 based on the voltage setpoint. The second offset
capacitive element CO2 allows the first voltage V1 to be higher
than a voltage at the second parallel amplifier output PAO2. As a
result, the second parallel amplifier 16 may at least partially
regulate the first voltage V1 in a proper manner even if the first
voltage V1 is greater than a maximum output voltage from the second
parallel amplifier 16 at the second parallel amplifier output
PAO2.
[0040] The power supply control circuitry 22 receives the DC source
signal VDC and is coupled to the first parallel amplifier 14, the
second parallel amplifier 16, and the switching circuitry 18. The
first inductive element L1 and the second inductive element L2
provide a second power supply output signal PS2 via the first
connection node 20. The first filter capacitive element C1 is
coupled between the first connection node 20 and a ground. The
first inductive element L1 is coupled between the switching
circuitry output SCO and the first connection node 20. The second
filter capacitive element C2 is coupled between a first end of the
second inductive element L2 and the ground. A second end of the
second inductive element L2 is coupled to the first connection node
20.
[0041] In general, the first filter capacitive element C1 is
coupled between the first parallel amplifier output PAO1 and the
ground. In the embodiment of the DC-DC converter 10 illustrated in
FIG. 2, the first filter capacitive element C1 is coupled between
the first parallel amplifier output PAO1 and the ground through the
first offset capacitive element CO1. In an alternate embodiment of
the DC-DC converter 10, the first offset capacitive element CO1 is
omitted, such that the first filter capacitive element C1 is
directly coupled between the first parallel amplifier output PAO1
and the ground. The first inductive element L1 and the first filter
capacitive element C1 form the first low-pass filter 24 having a
first cutoff frequency. The second inductive element L2 and the
second filter capacitive element C2 form the second low-pass filter
26 having a second cutoff frequency. The second cutoff frequency
may be significantly higher than the first cutoff frequency. As
such, the first low-pass filter 24 may be used primarily to filter
the switching output voltage VS, which is typically a square wave.
However, the second low-pass filter 26 may be used to target
specific high frequencies, such as certain harmonics of the
switching output voltage VS.
[0042] In a first embodiment of the first low-pass filter 24 and
the second low-pass filter 26, the second cutoff frequency is at
least 10 times greater than the first cutoff frequency. In a second
embodiment of the first low-pass filter 24 and the second low-pass
filter 26, the second cutoff frequency is at least 20 times greater
than the first cutoff frequency. In a third embodiment of the first
low-pass filter 24 and the second low-pass filter 26, the second
cutoff frequency is at least 50 times greater than the first cutoff
frequency. In a fourth embodiment of the first low-pass filter 24
and the second low-pass filter 26, the second cutoff frequency is
at least 100 times greater than the first cutoff frequency. In a
fifth embodiment of the first low-pass filter 24 and the second
low-pass filter 26, the second cutoff frequency is at least 200
times greater than the first cutoff frequency. In a sixth
embodiment of the first low-pass filter 24 and the second low-pass
filter 26, the second cutoff frequency is at least 500 times
greater than the first cutoff frequency. In a seventh embodiment of
the first low-pass filter 24 and the second low-pass filter 26, the
second cutoff frequency is at least 1000 times greater than the
first cutoff frequency. In an eighth embodiment of the first
low-pass filter 24 and the second low-pass filter 26, the second
cutoff frequency is equal to about 1000 times than the first cutoff
frequency. In a ninth embodiment of the first low-pass filter 24
and the second low-pass filter 26, the second cutoff frequency is
less than about 10,000 times than the first cutoff frequency.
[0043] FIG. 3 shows the DC-DC converter 10 according to an
additional embodiment of the DC-DC converter 10. The DC-DC
converter 10 illustrated in FIG. 3 is similar to the DC-DC
converter 10 illustrated in FIG. 2, except in the DC-DC converter
10 illustrated in FIG. 3, the first offset capacitive element CO1
and the second offset capacitive element CO2 are omitted.
Additionally, the first low-pass filter 24 further includes a first
resistive element R1 and the second low-pass filter 26 further
includes a second resistive element R2. The first resistive element
R1 and the first filter capacitive element C1 are coupled in series
between the first connection node 20 and the ground. The second
resistive element R2 and the second filter capacitive element C2
are coupled in series between the first end of the second inductive
element L2 and the ground. The second end of the second inductive
element L2 is coupled to the first connection node 20. By adding
the first resistive element R1 and the second resistive element R2,
Q Factors of the first low-pass filter 24 and the second low-pass
filter 26 may be reduced, respectively.
[0044] FIG. 4 shows the DC-DC converter 10 according to another
embodiment of the DC-DC converter 10. The DC-DC converter 10
illustrated in FIG. 4 is similar to the DC-DC converter 10
illustrated in FIG. 1, except in the DC-DC converter 10 illustrated
in FIG. 4, the switching supply 12 further includes a third
inductive element L3 coupled between the first parallel amplifier
output PAO1 and the first feedback input FBI1. As such, the second
inductive element L2 and the third inductive element L3 are coupled
in series between the first feedback input FBI1 and the second
feedback input FBI2. In one embodiment of the switching supply 12,
a second connection node 28 is provided where the third inductive
element L3 and the second inductive element L2 are connected to one
another. The first parallel amplifier 14 provides the first
parallel amplifier output current IP1 and a third voltage V3 to the
second connection node 28 via the first parallel amplifier output
PAO1. The third inductive element L3 has a third inductor current
IL3.
[0045] Further, in one embodiment of the first parallel amplifier
14, the first parallel amplifier 14 has a limited open loop gain at
high frequencies that are above a first frequency threshold. At
such frequencies, a group delay in the first parallel amplifier 14
may normally limit the ability of the first parallel amplifier 14
to accurately partially regulate the first voltage V1 of the first
power supply output signal PS1. However, by feeding back the second
voltage V2 to the first feedback input FBI1, a phase-shift that is
developed across the third inductive element L3 at least partially
compensates for the limited open loop gain of the first parallel
amplifier 14 at frequencies that are above the first frequency
threshold, thereby improving the ability of the first parallel
amplifier 14 to accurately partially regulate the first voltage V1.
In this regard, in one embodiment of the DC-DC converter 10, the
first parallel amplifier 14 partially provides the first power
supply output signal PS1 via the first parallel amplifier output
PAO1 based on the voltage setpoint and feeding back a voltage to
the first feedback input FBI1 from the first connection node 20
between the first inductive element L1 and the third inductive
element L3.
[0046] The first inductive element L1 has the first inductance and
the third inductive element L3 has a third inductance. In a first
embodiment of the first inductive element L1 and the third
inductive element L3, a magnitude of the first inductance is at
least 10 times greater than a magnitude of the third inductance. In
a second embodiment of the first inductive element L1 and the third
inductive element L3, a magnitude of the first inductance is at
least 100 times greater than a magnitude of the third inductance.
In a third embodiment of the first inductive element L1 and the
third inductive element L3, a magnitude of the first inductance is
at least 500 times greater than a magnitude of the third
inductance. In a fourth embodiment of the first inductive element
L1 and the third inductive element L3, a magnitude of the first
inductance is at least 1000 times greater than a magnitude of the
third inductance. In a fifth embodiment of the first inductive
element L1 and the third inductive element L3, a magnitude of the
first inductance is less than 1000 times greater than a magnitude
of the third inductance. In a sixth embodiment of the first
inductive element L1 and the third inductive element L3, a
magnitude of the first inductance is less than 5000 times greater
than a magnitude of the third inductance.
[0047] FIG. 5 shows the DC-DC converter 10 according to a further
embodiment of the DC-DC converter 10. The DC-DC converter 10
illustrated in FIG. 5 is similar to the DC-DC converter 10
illustrated in FIG. 4, except in the DC-DC converter 10 illustrated
in FIG. 5, the second feedback input FBI2 is coupled to the second
connection node 28 instead of being coupled to the second parallel
amplifier output PAO2. As such, a phase-shift across the second
inductive element L2 at least partially compensates for limited
open loop gain of the second parallel amplifier 16 at frequencies
above a second frequency threshold.
[0048] FIG. 6 shows the DC-DC converter 10 according to a
supplemental embodiment of the DC-DC converter 10. The DC-DC
converter 10 illustrated in FIG. 6 is similar to the DC-DC
converter 10 illustrated in FIG. 4, except in the DC-DC converter
10 illustrated in FIG. 6, the switching supply 12 further includes
a fourth inductive element L4 coupled between the second parallel
amplifier output PAO2 and the second feedback input FBI2. As such,
the second inductive element L2 and the fourth inductive element L4
are coupled in series between the first parallel amplifier output
PAO1 and the second parallel amplifier output PAO2. In one
embodiment of the switching supply 12, a third connection node 30
is provided where the fourth inductive element L4 and the second
inductive element L2 are connected to one another. The fourth
inductive element L4 and the second inductive element L2 provide a
fourth voltage V4 to the second feedback input FBI2 via the third
connection node 30. The fourth inductive element L4 has a fourth
inductor current IL4.
[0049] Further, in one embodiment of the second parallel amplifier
16, the second parallel amplifier 16 has a limited open loop gain
at high frequencies that are above a second frequency threshold. At
such frequencies, a group delay in the second parallel amplifier 16
may normally limit the ability of the second parallel amplifier 16
to accurately partially regulate the first voltage V1 of the first
power supply output signal PS1. However, by feeding back the fourth
voltage V4 to the second feedback input FBI2, a phase-shift that is
developed across the fourth inductive element L4 at least partially
compensates for the limited open loop gain of the second parallel
amplifier 16 at frequencies that are above the second frequency
threshold, thereby improving the ability of the second parallel
amplifier 16 to accurately partially regulate the first voltage V1.
In this regard, in one embodiment of the DC-DC converter 10, the
second parallel amplifier 16 partially provides the first power
supply output signal PS1 via the second parallel amplifier output
PAO2 based on the voltage setpoint and feeding back a voltage to
the second feedback input FBI2 from the third connection node 30
between the second inductive element L2 and the fourth inductive
element L4.
[0050] The second inductive element L2 has the second inductance
and the fourth inductive element L4 has a fourth inductance. In a
first embodiment of the second inductive element L2 and the fourth
inductive element L4, a magnitude of the second inductance is at
least 10 times greater than a magnitude of the fourth inductance.
In a second embodiment of the second inductive element L2 and the
fourth inductive element L4, a magnitude of the second inductance
is at least 100 times greater than a magnitude of the fourth
inductance. In a third embodiment of the second inductive element
L2 and the fourth inductive element L4, a magnitude of the second
inductance is at least 500 times greater than a magnitude of the
fourth inductance. In a fourth embodiment of the second inductive
element L2 and the fourth inductive element L4, a magnitude of the
second inductance is at least 1000 times greater than a magnitude
of the fourth inductance. In a fifth embodiment of the second
inductive element L2 and the fourth inductive element L4, a
magnitude of the second inductance is less than 1000 times greater
than a magnitude of the fourth inductance. In a sixth embodiment of
the second inductive element L2 and the fourth inductive element
L4, a magnitude of the second inductance is less than 5000 times
greater than a magnitude of the fourth inductance.
[0051] FIG. 7 shows a radio frequency (RF) communications system 32
according to one embodiment of the present disclosure. The RF
communications system 32 includes RF transmitter circuitry 34, RF
system control circuitry 36, RF front-end circuitry 38, an RF
antenna 40, and a DC power source 42. The RF transmitter circuitry
34 includes transmitter control circuitry 44, an RF power amplifier
(PA) 46, the DC-DC converter 10, and PA bias circuitry 48. In an
alternate embodiment of the RF communications system 32, the DC
power source 42 is external to the RF communications system 32.
[0052] In one embodiment of the DC-DC converter 10, the DC-DC
converter 10 functions as an envelope tracking power supply, which
provides power to the RF PA 46. As such, the first power supply
output signal PS1 is a first envelope power supply signal. In
envelope tracking systems, the first envelope power supply signal
is amplitude modulated to track an envelope of an RF transmit
signal RFT provided by the RF PA 46. As RF communications protocols
evolve, a bandwidth of the envelope of the RF transmit signal RFT
and a correlated bandwidth of the first envelope power supply
signal tend to increase to support increasing data bandwidths. In
this regard, the DC-DC converter 10 must support such increasing
bandwidths. Further, as RF communications protocols evolve, limits
on out-of-band RF emissions may become increasingly stringent.
Therefore, voltage accuracy of the first power supply output signal
PS1 may become increasingly important.
[0053] In one embodiment of the RF communications system 32, the RF
front-end circuitry 38 receives via the RF antenna 40, processes,
and forwards an RF receive signal RFR to the RF system control
circuitry 36. The RF system control circuitry 36 provides a power
supply control signal VRMP and a transmitter configuration signal
PACS to the transmitter control circuitry 44. The RF system control
circuitry 36 provides an RF input signal RFI to the RF PA 46. The
DC power source 42 provides the DC source signal VDC to the DC-DC
converter 10. Specifically, the DC power source 42 provides the DC
source signal VDC to the switching circuitry 18 (FIG. 1), the first
parallel amplifier 14 (FIG. 1), and the second parallel amplifier
16 (FIG. 1). In one embodiment of the DC power source 42, the DC
power source 42 is a battery. In one embodiment of the power supply
control signal VRMP, the power supply control signal VRMP is an
envelope power supply control signal.
[0054] The transmitter control circuitry 44 is coupled to the DC-DC
converter 10 and to the PA bias circuitry 48. The DC-DC converter
10 provides the first power supply output signal PS1 to the RF PA
46 based on the power supply control signal VRMP. Specifically, the
voltage setpoint of the first power supply output signal PS1 is
based on the power supply control signal VRMP. As such, the first
power supply output signal PS1 is a first envelope power supply
signal. The DC source signal VDC provides power to the DC-DC
converter 10. As such, the first power supply output signal PS1 is
based on the DC source signal VDC.
[0055] The power supply control signal VRMP is representative of
the voltage setpoint of the first power supply output signal PS1.
As such, the voltage setpoint is based on the power supply control
signal VRMP. The RF PA 46 receives and amplifies the RF input
signal RFI to provide the RF transmit signal RFT using the first
envelope power supply signal, which is the first power supply
output signal PS1. The first envelope power supply signal provides
power for amplification to the RF PA 46. The RF front-end circuitry
38 receives, processes, and transmits the RF transmit signal RFT
via the RF antenna 40. In one embodiment of the RF transmitter
circuitry 34, the transmitter control circuitry 44 configures the
RF transmitter circuitry 34 based on the transmitter configuration
signal PACS.
[0056] The PA bias circuitry 48 provides a PA bias signal PAB to
the RF PA 46. In this regard, the PA bias circuitry 48 biases the
RF PA 46 via the PA bias signal PAB. In one embodiment of the PA
bias circuitry 48, the PA bias circuitry 48 biases the RF PA 46
based on the transmitter configuration signal PACS. In one
embodiment of the RF front-end circuitry 38, the RF front-end
circuitry 38 includes at least one RF switch, at least one RF
amplifier, at least one RF filter, at least one RF duplexer, at
least one RF diplexer, at least one RF amplifier, the like, or any
combination thereof. In one embodiment of the RF system control
circuitry 36, the RF system control circuitry 36 is RF transceiver
circuitry, which may include an RF transceiver IC, baseband
controller circuitry, the like, or any combination thereof. In one
embodiment of the RF transmitter circuitry 34, the first envelope
power supply signal provides power for amplification and envelope
tracks the RF transmit signal RFT.
[0057] FIG. 8 shows the RF communications system 32 according to an
alternate embodiment of the RF communications system 32. The RF
communications system 32 illustrated in FIG. 8 is similar to the RF
communications system 32 illustrated in FIG. 7, except in the RF
communications system 32 illustrated in FIG. 8, the RF transmitter
circuitry 34 further includes a digital communications interface
50, which is coupled between the transmitter control circuitry 44
and a digital communications bus 52. The digital communications bus
52 is also coupled to the RF system control circuitry 36. As such,
the RF system control circuitry 36 provides the power supply
control signal VRMP (FIG. 7) and the transmitter configuration
signal PACS (FIG. 7) to the transmitter control circuitry 44 via
the digital communications bus 52 and the digital communications
interface 50.
[0058] FIG. 9 shows details of the DC-DC converter 10 illustrated
in FIG. 7 according to one embodiment of the DC-DC converter 10.
The DC-DC converter 10 includes the power supply control circuitry
22, the first parallel amplifier 14, the second parallel amplifier
16, and the switching supply 12. The power supply control circuitry
22 controls the first parallel amplifier 14, the second parallel
amplifier 16, and the switching supply 12. Each of the first
parallel amplifier 14, the second parallel amplifier 16, and the
switching supply 12 at least partially provides the first power
supply output signal PS1.
[0059] FIG. 10 shows the RF communications system 32 according to
another embodiment of the RF communications system 32. The RF
communications system 32 illustrated in FIG. 10 is similar to the
RF communications system 32 illustrated in FIG. 7, except in the RF
communications system 32 illustrated in FIG. 10, the PA bias
circuitry 48 (FIG. 7) is not shown and the RF PA 46 includes a
driver stage 54 and a final stage 56, which is coupled to the
driver stage 54. The DC-DC converter 10 provides the second power
supply output signal PS2, which is a second envelope power supply
signal, to the driver stage 54 based on the power supply control
signal VRMP. Further, the DC-DC converter 10 provides the first
power supply output signal PS1, which is the first envelope power
supply signal, to the final stage 56 based on the power supply
control signal VRMP. The driver stage 54 receives and amplifies the
RF input signal RFI to provide a driver stage output signal DSO
using the second envelope power supply signal, which provides power
for amplification. Similarly, the final stage 56 receives and
amplifies the driver stage output signal DSO to provide the RF
transmit signal RFT using the first envelope power supply signal,
which provides power for amplification.
[0060] Some of the circuitry previously described may use discrete
circuitry, integrated circuitry, programmable circuitry,
non-volatile circuitry, volatile circuitry, software executing
instructions on computing hardware, firmware executing instructions
on computing hardware, the like, or any combination thereof. The
computing hardware may include mainframes, micro-processors,
micro-controllers, DSPs, the like, or any combination thereof.
[0061] None of the embodiments of the present disclosure are
intended to limit the scope of any other embodiment of the present
disclosure. Any or all of any embodiment of the present disclosure
may be combined with any or all of any other embodiment of the
present disclosure to create new embodiments of the present
disclosure.
[0062] Those skilled in the art will recognize improvements and
modifications to the embodiments of the present disclosure. All
such improvements and modifications are considered within the scope
of the concepts disclosed herein and the claims that follow.
* * * * *